Air Tightness Test

Ultrasonic leak detection takes advantage of the fundamental characteristics and properties of sound waves to identify and precisely locate air leaks in any structure. The air test performed makes use of the reflection and absorption of sound waves when incident on a boundary between a solid structure and the air adjacent to it making it the perfect air pressure test.

Ultrasonic leak detectors are comprised of two main components: an ultrasound generator, and a receiver unit. The generator is placed on one side of a structure and switched on, filling the room or compartment with ultrasound. The receiver is then deployed on the other side of the structure to scan the structure for leaks.

When no leak is present, the ultrasound is reflected or absorbed by the structure and so no ultrasound is detected by the receiver. In contrast, when the receiver wand is pointed towards a leak, ultrasound is detected, as it is able to propagate through the leak path in the structure. The precise location of the leak site can be determined by identifying the point in the seal with the maximum readings. Furthermore, the reflection and diffraction of the sound wave as it passes through the leak are affected by the size and shape of the leak, so information about these properties can be interpreted by the receiver. This helps prevent uncontrolled air leakage.

Why is Airtightness Important?

Fire safety: When dealing with fire suppression for server rooms, data centres or other high-value assets, it is important to use gaseous fire suppression systems (i.e., CO2, Inergen®, FM200®, NOVEC™ 1230), as these are clean systems that will not leave residue or damage the assets. For such systems, airtightness is of critical importance. This is because these systems rely on the fire extinguishing gas being contained for long enough to deprive the fire of oxygen and ensure it is fully extinguished. If the room containing the asset has unwanted air leaks, then this may not be achieved, and the fire may spread, causing damages, data loss and, in the worst cases, loss of life.

Improving indoor air quality: Indoor air quality has been a growing concern for some time, and rightly so, with many people spending as much as 90% of their time indoors. Especially important for commercial buildings post COVID19. Various solutions have been developed to filter and clean air more effectively, such as HEPA filters or ultraviolet filtration systems, but these processes can only be as effective as the ventilation in the building. In order to have adequate ventilation, it is vital that the building has controlled airflow, and that means eliminating unwanted leak sites.

Reducing energy usage: When heating or cooling a building, airtightness and ventilation is very important to combat poor energy efficiency. If a building is not sufficiently airtight, even with insulation, temperature control will be considerably less efficient with increased heating bills. This has two major implications: an increased carbon footprint and increased operating costs for your building as per building regulations. With an ever-increasing environmental awareness and energy bills, and campaigns around the world for more building for a sustainable future, airtightness has never been more important in the built environment and within new buildings. This is highly important for energy efficiency of buildings and using the Portascanner® AIRTIGHT 520 to detect air leakage during the construction phase of a building will significant impact energy performance.

Advantages to Using Ultrasound for Air Pressure Testing

Typical air test carried out involve pressurising the room or compartment and using either a pressure difference meter or air flow measurement devices to monitor its leakage rate. This process is highly intrusive and disruptive, often requiring the room/compartment to be evacuated prior to testing and considerable downtime post testing. Air pressure testing can also be expensive, and if your room fails this test, it must be fixed and retested until it passes.

Ultrasonic, acoustic leak detection is non-destructive and can be done quickly, with almost no disruption to normal operation, and provides clear diagnosis of any issues on the same day. This allows you to carry out an independent airtightness testing scheme and find and deal with repairs ahead of the pressurisation test, so you can be sure you will pass first time without uncontrolled flow of air.

Furthermore, pressurisation tests only provide information on the overall leakage rates in the room/compartment, and not on where these leaks are occurring. Our ultrasonic leak detectors enable you to easily identify, locate and even quantify individual leak sites, such as gaps and cracks, so you can target any remedial work in the areas it is most needed, improving the efficiency and effectiveness of building control.

Air Flow Rate Versus Air Permeability

When considering individual air leaks, and how much of a problem they will be, we can first consider the flow speed of air at a given pressure differential. From the flow speed, if we know the cross-sectional area of the leak, we can take this a step further and calculate a volumetric flow rate, which answers the question “How much air will leak through this hole?”. However, this question and its answer do not tell the full story when we are dealing with airtightness in a room or compartment. 

The relative scale of the problem from air coming through a given leak will cause depends intrinsically on the size of the room/compartment that the air is leaking into or out of. For this reason, the metrics that we use are not simple air flow rates, but air leakage rates. Typically, these are air permeability, which depends on the envelope area of the room; or air changes per hour, which depends on the volume of the room as well the total rate of air flow through all leaks. The Portascanner® AIRTIGHT 520 will automatically collate all the data from each air test of each structure tested in a room and provide an air permeability and air changes per hour value for each room. This can be compared against the design air permeability. The Portascanner® AIRTIGHT 520 is therefore ideal for air permeability testing across the entire building.

Example Case Study – Oxygen Reduction System, UK

Oxygen Reduction System had a UK server room with a floor area of approximately 91m2. The room was tested with the Portascanner® ultrasonic room integrity tester and points with high readings were noted. This test identified all the main sources of air leakage in the room, thus allowing targeted maintenance work to be carried out. After this maintenance had been conducted, assuming no further changes are made to the room, this room will retain its airtight integrity. Therefore, alongside the required, periodic checks of the room, the Portascanner® gives a high level of confidence that the room will comply with and exceed current ISO 14520 regulations along with other building regulations through our blower door testing equipment.